The Czochralski growth of doped bismuth-germanium oxide (BGO) and bismuth-silicon oxide (BSO) single crystals

Doped single crystals of BGO and BSO with Cr, Mn, Cu, Ni have been grown. The conditions for the growth of doped single crystals by the Czochralski method have been determined, analyses of distributions of dopants in the crystals have been made. For the Mn, Cr, Cu, doped crystals changes of coloration after illumination with visible light have been observed.     

Morphology of PbI2 Crystals Grown by Gel Method

The single crystals of Lead Iodide have been grown by gel method. X‐ray diffraction studies on these crystals shows that the lattice parameters of grown crystals are almost matching with reported values. The results of detailed studies made on the microstructures of Lead Iodide crystals, have been described. The observations of the faces of these crystals revealed that they have grown by layer as well as spiral mechanisms. The probable role of these parameters is explained along with the surface microstructures on these various shaped crystals.     

Stoichiometric dependence of electrical characteristics in WSSe single crystals grown by direct and chemical vapour transport techniques

Single crystals of tungsten sulphoselenide (WSSe) have been grown by both direct and chemical vapour transport techniques. The crystals have been subjected to Hall effect and resistivity measurements for their electrical characterization. The observed differences in the electrical resistivity, type of conduction, and activation energy have been attributed to the stoichiometric differences between the crystals grown by the two techniques. The crystals grown by chemical vapour transport technique with iodine as the transport agent have been found to be more stoichiometric.     

Microstructures of gel-grown ammonium hydrogen tartrate single crystals

Single crystals of ammonium hydrogen tartrate (AHT) have been grown in silica gels by employing the controlled reaction between ammonium chloride and tartaric acid. Transparent AHT crystals upto 24 × 4 × 3 mm³ in size have been grown at room temperature. Optical and electron-optical studies have been made on the various surface structures of {010} faces of the grown crystals. A variety of growth striations and growth hillocks have been observed. Growth layers modified by the presence of misaligned microcrystals have been illustrated. It has been suggested that two-dimensional nucleation, spreading and pilling up of growth layers is mainly responsible for the growth of these crystals and the implications are discussed.     

Ionic conductivity studies in KCl–NaCl mixed crystals

Single crystals of KCl and a few compositions of KCl-NaCl mixed crystals were grown from melt by Kyropoulos technique. Ionic conductivity measurements have been carried in these crystals in the temperature range 100 to 400 °C. The activation energy for the migration of charge carriers have been calculated from the conductivity-temperature plots of these crystals and the results obtained were discussed.     

Growth, phase transitions and properties of Li2Ti3O7 crystals

Metastable crystals of Li₂Ti₃O₇ of dimensions up to a diameter of 20 mm and a length of 20 mm have been grown by the Czochralski method from oriented seeds. The effects of seed orientation, growth atmosphere and dopant on crystal growth have been studied. Phase transition processes in the crystals and the H phase structure have been measured. Optical and acoustic properties of the crystals have also been determined.     

Micro- and nanostructures in lithium niobate single crystals doped with lanthanides

Lithium niobate single crystals doped with lanthanides (Gd, Er) and nominally pure single crystals of congruent and stoichiometric compositions have been grown under time-dependent thermal conditions. Regular growth domain microstructures and periodic nanostructures have been investigated by optical microscopy and atomic force microscopy with a step from 10 to 100 nm. Comparative investigations of the Raman spectra of lithium niobate single crystals of different compositions have been performed.     

Investigations of the growth mechanism and morphology of silver crystals grown electrolytically in gels

Gel medium has been used for the electrolytic growth of silver dendrites and single crystals of a variety of morphological features and forms. Microtopographic studies of the crystals have been carried out using optical and scanning electron microscopes. Some unusual growth surface morphologies have been observed. The surfaces of some of the crystals have a high degree of perfection. Sufficient experimental evidences are obtained for the striated growth of crystals and twin plane re-entrant edge (TPRE] mechanism of growth. The formation of tertiary three-dimensional (T3D) dendrites and dendrites with obliquely forward and backward branchings at different stages of growth have been investigated.     

Electrical and photoelectrical properties of chalcopyrite n-AgInS2 crystals

The chalcopyrite n-type crystals have been grown from AgInS₂ material having stoichiomtric Ag excess. The temperature dependence of the Hall effect in these crystals have been studied. The ionization energies of donors have been determined. The dependence of the photoconduction on the photon energy, the light intensity and the temperature in the n-AgInS₂ crystals have been measured. The recombination model of photoconductor with one class of recombination centres has been proposed for explanation of the photoelectrical results.     

Growth of Gallium Orthophosphate Single Crystals under Hydrothermal Conditions

Gallium orthophosphate (GaPO₄) single crystals have been grown from phosphoric acid solutions under hydrothermal conditions. The crystals have been studied in terms of twinning because of the strong effect of this structural defect on the piezoelectric properties. The growth rates of individual faces have been compared to each other by considering the dipyramidal habit of the grown crystals.     

Effect of Flux on thermoluminescence in Flux-grown BaFCl crystals

BaFCl crystals have been grown using BaF₂ and BaCl₂ by flux technique. Glow curves, optical absorption, and TL emission spectra of x/r — irradiated crystals are studied. The results have been compared with those BaFCl crystals grown from NaF flux so as to study the effects of flux on these properties. It is found that crystals grown from BaF₂ flux are relatively purer. An additional TL glow peak at 460 K, an optical absorption band at 775 nm and TL emission band at 485 nm have been obtained in the presently grown crystals. The additional glow peak, optical absorption band have been attributed to F(¯F) aggregate centers, whereas the 485 nm TL emission band to impurity centers.     

Surface structures of fluorite crystals

Optical studies have been made of the microstructures on the natural {100} and {111} faces of natural fluorite crystals. The protrudance of triangular elevations, growth pyramids, and natural etch pits have been observed on a large number of crystals. It is suggested that fluorite crystals grown by two-dimensional spreading and piling of growth layers parallel to {100} faces. The natural etch pits on {100} and {111} faces suggest that they have been produced as a result of a dissolution process in nature. The natural faces have been etched in the laboratory and it is established that the pits indicate the existence of linear defects in the crystals. The implications are discussed.     

PVT and CVT Growth and Characterization of SnSxSe2-x (0 ≤ x ≤ 2) Single Crystals

Single crystals of solid solutions of tin sulphoselenide have been grown in the same ampoule. Specific conditions for growing single crystals of SnSSe have also been identified. A study of microstructures on the growth surfaces responds to the mechanism of growth of these crystals. The dependence of electrical resistivity, Hall mobility and carrier concentration with the values of the configuration parameter 2 has been studied.     

Synthesis and growth of PbTe crystals at low temperature and their characterization

Lead telluride crystals have been grown for the first time by the cold traveling heater method. The structural properties of the crystals have been studied by neutron diffraction, and rocking-curves with a full-width at half-maximum of about 36 arcsec have been measured, indicating a very weak mosaicity. The lattice parameter of the crystals has been found to be ∼0.64618±0.00004 nm by X-ray diffraction. Vickers microhardness in the range 25–30 kg/mm² have been measured, depending on the charge applied to the crystals. The electronic properties of the crystals, either as-grown or annealed, have been measured and demonstrate their very high purity level, as expected from the low-temperature growth and purification process by traveling heater method. Finally, the potentialities of PbTe as a substrate for the growth of HgCdTe layers are discussed in the light of all the results reported.     

Microstructures on {111} faces of stannic iodide single crystals

Single crystals of stannic iodide (SnI₄) havebeen grown using the controlled reaction between SnCl₂ and KI by diffusion process in silica gel medium. Orange to reddish octahedral stannic iodide crystals up to 3–4 mm in size have been grown at room temperature. Optical studies have been made on the various surface structures of {111} faces of the asgrown crystals. On octahedral faces of these crystals, triangular-shaped hillocks with growth layers in the 〈110〉 directions have been observed. Occasionally, growth spirals on octahedral faces have also been reported. Close loops of growth fronts have been investigated and have been interpreted. It has been suggested that two-diemensional nucleation, spreading and pilling up of triangular growth layers is mainly responsible for the growth and occasionally the growth is due to screw dislocations. The implications are discussed.     

PVT and CVT Growth and Characterization of SnSxSe2-x (0 ⩽ <x 2) Single Crystals

Single crystals of solid solutions of tin sulphoselenide have been grown in the same ampoule. Specific conditions for growing single crystals of SnSSe have also been identified. A study of microstructures on the growth surfaces responds to the mechanism of growth of these crystals. The dependence of electrical resistivity, Hall mobility, carrier concentration with the values of the configuration parameter x has been studied.     

Physico-chemical properties of pure and x-ray irradiated single crystals of KAP

Single crystals of potassium hydrogen phthalate (KAP) have been grown by slow evaporation method from aqueous solutions. Thermal analyses indicate that KAP crystals decompose into phthalic anhydride and KOH around 520 K. Electrical properties of single crystals of KAP have been studied along with the effect of X-ray irradiation of the crystals. The electrical transport appears to be associated with tunneling of protons. The irradiated crystal exhibits lower dielectric constant and higher ac conductivity.     

Growth and properties of calcium tungstate

CaWO₄ single crystals have been grown and compared by three different high temperature solution methods, viz. the normal flux-cooling procedure, the indirect flux-reaction technique and the isothermal flux-evaporation method. The typical as-grown bipyramidal crystals obtained by these methods have been found to be mostly large and perfect with varying degree of transparency. The crystals are characterised by using EDAX, X-ray diffraction, electrical conduction, micromechanical tests and chemical etching. The assessment of various characteristics of the grown crystals is likely to show enormous usefulness of the flux grown crystals.     

Structure perfection of some molecular crystals grown from the melt

Single crystals of anthracene, naphthalene, phenazine and anthracene sym. trinitrobenzene (TNB) were examined using X-ray topography. Low-angle boundaries were observed and misorientation vectors of adjacent mosaic blocks have been estimated. Using an X-ray camera with oscillating film dislocation density in crystals has been evaluated. Anthracene-TNB crystals showed a much higher structure perfection than the other crystals.